Normally, an electric drive comprises an electric machine (i.e., electric motor) as well as a subsequent reduction gearing that translates a rotational movement from fast to slow. The reduction gearing transfers the torque to the driveline of the motor vehicle. For this, a differential gearing arranged downstream the reduction gearing in the power path splits up the introduced torque to the two output shafts for driving the vehicle wheels. The two output shafts of the differential gearing have a compensating effect relative to each other, i.e. if one of the two output shafts rotates faster, the other output shaft rotates correspondingly slower and vice versa.
From WO 2012 007031 A1 an electric drive for a motor vehicle is known, which electric drive comprises an electric motor and a transmission unit. The transmission unit comprises a planetary gearing and a differential gearing which are arranged coaxially relative to one another. There is provided a manual clutch which can be transferred into three switching positions, i.e., two different switching positions and one idling position.
From DE 11 2006 001 851 T5 an auxiliary drive assembly for a motor vehicle is known. Said drive assembly comprises an electric motor, a planetary reduction gearing and a differential gearing which are arranged coaxially relative to one another. The planetary gearing comprises a carrier which is driven by the electric motor, and a plurality of flange shafts which are connected to the carrier and which each freely rotatably carry pairs of first and second planetary gears firmly connected to each other. The first planetary gears have a smaller diameter than the second planetary gears and engage the teeth of a stationary sun gear. The second planetary gears engage larger planetary gears which are rotatably supported on further flange shafts connected to the carrier. The larger planetary gears engage the second sun gear which is connected so as to be rotationally fixed to the differential cage of the differential gearing.
DE 11 2010 005 738 T5 proposes an electric drive having an electric motor, a traction drive, a planetary gearing and a differential gearing. The driving axle of the electric motor and the rotational axis of the differential gearing are offset relative to each other.
From De 10 2011 004 698 A1 an electric drive is known having an electric motor, a planetary gearing and a differential gearing which are arranged coaxially relative to one another.
From DE 1 116 543 A an axle unit is known having its own driving motor and a differential gearing.
From DE 10 2010 054 533 A1 a transmission is known having a reduction portion and a differential portion. The reduction portion comprises two planetary stages. The differential portion is configured as a spur gear differential.
From DE 10 2005 004 290 A1 a transmission module is known for variably distributing torque in the driveline of a motor vehicle. The transmission module comprises a first shaft having a first sun gear, a second shaft having a second sun gear, a plurality of planetary gears which engage the first sun gear and the second sun gear and a carrier element carrying the planetary gears. By means of a clutch, the carrier element can be connected to a stationary housing, so that torque is transmitted between the first and the second shaft.
In the case of drive concepts comprising an electric drive, currently there is a development trend towards electric machines with higher rotational speeds, which, in turn, requires the use of higher transmission ratios of a subsequent reduction gearing. Such transmission ratios cannot necessarily be achieved by a two-stage spur gear transmission. At the same time, higher rotational speeds of the electric drives intensify the risk of an undesirable NVH (noise, vibration, and harshness) behaviour and greater splashing losses in the transmission. According to a common understanding, NVH behaviour includes an oscillation which is audible as a noise and/or sensible as vibration and which is usually undesirable.